{
CFMetaData oldCfm = ThriftValidation.validateColumnFamily(keyspace(), columnFamily());
boolean columnExists = false;
// mutating oldCfm directly would be bad, but mutating a Thrift copy is fine. This also
// sets us up to use validateCfDef to check for index name collisions.
CfDef cf_def = oldCfm.toThrift();
for (ColumnDef cd : cf_def.column_metadata)
{
if (cd.name.equals(columnName.key))
{
if (cd.index_type != null)